How Climate Change is Affecting Maple Syrup Production

Research by the Proctor Maple Research Center at the University of Vermont indicates that climate change has had an effect on maple syrup production.  According to the Center, the Vermont maple sugaring season on average starts 8.3 days earlier and ends 11.6 days earlier than it did 50 years ago. The transition from winter to summer is shorter, representing approximately 10% of the sugaring season in Northern New England.

A shorter season affects the production of maple sap (which is boiled down to make syrup) in a couple of ways. Alternating freezing and thawing cycles, which take place in late winter, control the flow of maple sap. Fewer freezing and thawing cycles mean the maple trees produce less sap. In addition, maple trees rely on snowpack during this time to protect their roots from freezing. Less snow can potentially affect the health of sugar maple trees.

“Climate change definitely will, and already has, had an effect on the maple syrup industry,” said Timothy Perkins, Ph.D., director of the Proctor Maple Research Center. “We are fortunate in that technological advances in maple sap collection have, so far, out-paced any losses we may have experienced due to the loss of season duration.  In the long-term, we are unsure how climate change will impact the maple industry, or what our response might be, however we are looking at several novel approaches to collecting sap with the hope that we will be able to reduce the impacts of climate change on maple syrup production for as long as possible.”

Northern Migration of Maple Trees

Research also shows a long-term impact of climate change may be a shift in forest migration across the Northeast with maples and birches moving north and parts of New England developing an oak-pine forest system.

“In general, plants live where they do based upon the temperature and precipitation regime.  Different plants have different tolerances for environmental conditions.  These may affect lots of different aspects of a plant’s life strategy: germination, early establishment, growth, photosynthesis, respiration, etc.,” said Perkins. “If it gets warmer, and there is more or less precipitation in an area, then different assemblages of species than currently live in an area will have an increased competitive advantage over those that are there.  Over this, the species more adapted to these new environmental (climatological) conditions will begin to out compete the plants that are already there, with the result that the plant communities in an area will shift over time as some species are replaced by others.”

“The ecological niche is changing already (longer growing season for example), but that does not mean the trees will die,” said Ivan J. Fernandez, distinguished Maine professor at the University of Maine’s School of Forest Resources and Climate Change Institute. “There are a lot of things that cause the actual tree species to change, like slower forest regeneration with natural processes of mortality of old trees followed by young trees coming in under that canopy.  It is at that stage that new species may occupy the site if the niche has been altered.  The maps you see show about 100 years ahead where species ranges will shift somewhat north. However, fire, wind, insects and disease can cause catastrophic changes that take place very quickly, and those we have a lot less ability to predict.  If there is a young healthy maple out back today, it very well may live its life out to the fullest.  It may not be replaced, however, by another maple.”

Causes for Sugar Maple Decline: Extreme Weather, Acid Rain and Insect Threats

Fernandez believes the rate of climate change warrants special attention, noting that if the trajectory stays the same, climate change will increasingly cause incidences of extreme weather such as drought and intense precipitation. Climate change is caused by the burning of fossil fuels (such as coal, oil, and gas), which release greenhouse gases into the atmosphere and in turn raise global temperatures and alter weather patterns. According to Fernandez, while the emission of greenhouse gases in developed countries is declining, there is an increase in usage by developing countries like China.

Acid deposition (more commonly known to the public as “acid rain” is the environmental consequence of burning fossil fuels. Acid deposition (which includes all acidifying substances and forms coming out of the atmosphere such as acid rain, snow, fog, sleet, hail, as well as dry gases and particles of these chemicals) contains higher than normal amounts of nitric and sulfuric acids, which are depleting calcium nutrients in maple hardwoods. Sugar maples require a lot of nutrients in their soil to help them grow, cope with disease, and provide internal signaling (i.e. when to seal off decay or injury, when to take up water).

Since 1995 Scott Bailey (a geologist/soil scientist) has worked with Steve Horsley (a forest physiologist), Bob Long (a plant pathologist), and Rich Hallett (an expert in foliar chemistry) on studying sugar maple health and growth in relation to nutrition and stress in the northeastern United States. Their findings thus far show sugar maple decline has been more common in the last 40 years or so due to a predisposing nutrient imbalance (an inadequate amount of calcium and magnesium in the soil primarily caused by acid rain) compounded by an inciting secondary stress (i.e. insect defoliation and deep soil freezing).

An example of secondary stress on maple trees occurs when insects such as Forest Tent caterpillars invade a forest. Beginning in late summer, sugar maple trees begin storing excess starches. The starch is stored until spring  when warming temperatures convert it to sugars. In a process known as photosynthesis, the green leaves of a sugar maple tree use sunlight to convert starches into sugars. When defoliating insects damage the leaves of a sugar maple tree by eating them, they remove the photosynthetic tissue critical for plant maintenance and growth.

Bailey believes climate change and milder winters contribute to the insect infestations threatening sugar maples. Historically, native insects are on a cycle of population growth and decline every 10 – 20 years. “What’s been happening instead,” Bailey said, “ is that species are going away and coming back every 3-4 years.”  The good news is that research shows maples are resilient if the soil is good and contains adequate nutrition.

There was no need to tell the maple farmers that change was afoot. “We could tell first hand on our farm that climate change was happening,” said seventh-generation maple syrup producer Arnold Coombs. “As a rule of thumb, we would never tap before town meeting day (first Tuesday in March), it was just too cold. But year after year it would warm up earlier. We’re now tapping in mid-February so we don’t miss any of the season.”

Coombs added, “I remember one year when my father made syrup in May. We now often don’t even get to April.”